1. Field of the Invention
The invention relates generally to tissue cauterization. More particularly, the invention relates to an improved electrode for tissue cauterization.
2. Description of the Background Art
Tissue and organ removal are required in a number of surgical procedures for a number of purposes. A major concern in all tissue removal procedures is hemostasis, ie. cessation of bleeding. All blood vessels supplying an organ or a tissue segment to be removed have to be sealed, either by suturing or cauterization, to inhibit bleeding when the tissue is removed. For example, when the uterus is removed in a hysterectomy, bleeding must be inhibited in the cervical neck which is resected, as well as along the vessels which supply blood to the uterus along its sides. Similarly, blood vessels within the liver must be individually sealed when a portion of the liver is resected in connection with removal of a tumor or for other purposes. The liver is a highly vascularized organ and sealing of the blood vessels is quite time consuming. Achieving hemostasis is necessary in both open surgical procedures and in minimally invasive surgical procedures. In the latter case, however, because of the limited access through cannula and other small passages, sealing of blood vessels can be even more time consuming and problematic.
Achieving hemostasis is particularly important in laparoscopic and other limited access procedures where the organ or other tissue must be morcellated prior to removal. Most organs are too large to be removed intact through a cannula or other limited access passage, thus requiring that the tissue be morcellated, e.g. cut, ground, or otherwise broken into smaller pieces, prior to removal. It will be appreciated that morcellation of vascularized tissue can be very problematic.
For these reasons, it would be desirable to provide improved methods, systems, and apparatus, for achieving hemostasis in connection with organ and tissue removal procedures. In particular, it would be desirable to provide methods and systems which permit a surgeon to achieve hemostasis in a time-efficient manner, using readily available surgical equipment e.g. radio frequency power supplies as discussed below, while reducing risk and trauma to the patient. It would be further desirable if the methods and systems are applicable to a wide variety of tissue removal procedures, including at least hysterectomies, liver tissue resection, cholecystectomies, prostate removal, lung resection, and the like. It would be still further desirable if the methods could provide for complete or substantially complete coagulation and hemostasis of an entire volume of tissue to be removed to facilitate such procedures as a subsequent morcellation. The ability to, for example, morcelate tissue while minimizing bleeding will be of substantial benefit to the performance of laparoscopic and other minimally invasive procedures, as well as other surgical procedures.
The use of radio frequency (RF) energy to necrose body organs or portions thereof is known. U.S. Pat. No. 4,979,948 describes a balloon electrode which is inflated in the interior of a uterus and used to apply RF energy to necrose the endothelial lining of the uterus. U.S. Pat. No. 3,845,771 describes a glove having flexible electrodes on the thumb and middle finger. The glove is intended for conducting RF current to conventional forceps, scalpels, etc. U.S. Pat. No. 4,972,846 describes electrode patch pairs useful as defibrillator leads which are engaged directly on the epicardium. U.S. Pat. Nos. 5,178,618 and 5,078,736 describe stents which can be energized to apply RF energy on the interior of a body lumen. Lorentzen et al. (1996) Min. Ivas. Ther. Allied Technol. 5:511-516 describes a loop electrode that can be rotated within tissue to excuse a tissue volume.
U.S. Pat. No. 6,203,541 discloses an automatic circuit that controls a surgical instrument, having a pair of bipolar electrodes. The circuit comprises a means for measuring the current between the pair of electrodes, an impedance detection circuit that is in electrical communication with the current measuring means, a comparator that has an electrical communication with the impedance detection circuit, and a controller that is electrically connected to the comparator. The impedance detection circuit calculates the impedance between the electrodes based on the measured currents and generates a first signal indicative of the calculated impedance. The comparator processes the first signal and generates an activation signal if the calculated impedance falls within a predetermined range of impedance values and generates a deactivation signal if the calculation impedance exceeds a deactivation threshold. The controller receives the activation and deactivation signals and transmits the first control signal to a radio frequency energy output stage to activate the electrodes in response to the activation signal and transmits the second control signal to the radio frequency output stage to deactivate the electrodes in response to the deactivation signal.
U.S. Pat. No. 6,398,779 teaches a method for electrosurgically sealing a tissue that concludes the steps of applying an initial pulse of RF energy to the tissue, the pulse having characteristics selected so as not to heat the tissue appreciably; measuring the value of the impedance of the tissue and response to the applied pulse; and in accordance with the measured impedance value, determining an initial set of pulse parameters for use during a first RF energy pulse as applied to the tissue. The invention teaches varying the pulse parameters of individual ones of subsequent RF energy pulses in accordance with at least one characteristic of an electrical transient that occurs during subsequent RF energy pulses. The method terminates the generation of subsequent RF energy pulses upon a determination that the electrical transient is absent or that a minimum output voltage has been reached.
U.S. Pat. No. 5,443,463 teaches a coagulating forceps for selectively coagulating blood vessels or tissue containing blood vessels. The method taught involves the placement of the blood vessels or tissue containing blood vessels between the prongs of the forceps, with the jaws of the forceps containing a plurality of electrodes which are energized by radio frequency power. A plurality of sensors are associated with the electrodes, and in contact with the vessels or tissue, to measure the temperature rise of the tissue or blood vessels and to provide a feedback to the radio frequency power to control the heating to perform coagulation of vessels or tissue. The invention also teaches that the upper prong of the device may be split into two parts with the cutting blade between the two upper parts to provide for cutting of the coagulated vessels subsequent to the coagulation.